The use of nitro-para phenylenediamine derivatives for use in the dyeing of keratinic (hair) fibers is known in the art as is reflected in U.S. Pat. No. 3,549,303 (1974) and U.S. Pat. No. 3,925,474 (1975), both held by L'Oreal, S. A.
The prior art, as is reflected in the above, as well as in other compositions used in hair coloration, suffer from a common disadvantage, that being damage to many hair types and a permanent character of the hair coloration. This for many consumers is an undesirable aspect of the use of hair dyes. Due to the relatively low molecular weight of prior art keratinic dyes, such compounds are able to penetrate the cuticle of the hair prior art keratinic dyes, such compounds are able to penetrate the cuticle of the hair thereby rendering it difficult to remove without use of harsh and potentially damaging stripping agents. Also, it is believed that hair coloring agents that penetrate the cuticle are inherently harmful to the hair regardless of whether or not the user wishes to remove or change the hair color. Many advantages could be associated with a hair coloring agent having a molecular weight sufficiently high such that a hair dye, incorporating such a high molecular weight agent therein, would not penetrate the keratinic fiber, or at least would not penetrate the fiber to the extent of lower molecular weight agents, thereby producing a true temporary or semi-permanent hair coloring agent, that is, one having increased ease of removal.
Where the instant derivative of 4-nitro-m-phenylenediamine is not used as the sole hair coloring agent, it is believed that it can be advantageously mixed with traditional higher molecular weight dyes to reduce the above set forth disadvantages of the prior art while Imparting to a resultant hair dye substantially all of the advantages and objectives as above set forth herein.
In the prior art, as best known to the within inventors, a usable meta bond within a 4-nitro-m-phenylenediamine (hereinafter "4-NMPD") is not known nor is any combination of 4-NMPD with a sulfate to form the present inventive molecular structure, that is, 4-NMPD sulfate.
As is more fully set forth below, it is the addition of the sulfate radical which provides to the inventive molecule its resultant high molecular weight, that is, a molecular weight in the range of 251 to 349.